Stiff leg derrick



Sept. 1 1964 R. P. FOX ETA].

swm LEG DERRICK 3 Sheets-Sheet 1 Filed Dec. 3, 1962 M MXW M m w m mF o n N2 L .F m

R. P. Fox ETAL 3,148,778

Sept. 15, 1964 STIFF LEG DERRICK 5 Sheets-Sheet 2 Filed Dec. 3, 1962 F IE: 5

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BY Bimmm: damslrrakvzrs Sept. 15, 1964 R. P. FOX ETAL STIFF' LEG DERRICK Filed D80. 3, 1962 3 Sheets-Sheet 3 Rosa-R7 P Fox BY Rama/w A Evssrm WWW aux...

United States Patent O 3,148,778 STIFF LEG DERRICK Robert P. Fort, St. Paul, Minn., and Raymond A. Engstrom, Hudson, Wis, assiguors to American Hoist & Derrick Company, St. Paul, Minn., a corporation of Delaware Filed Dec. 3, 1962, Ser. No. 241,577 Claims. (Ci. 2127tl) The present invention has relation to stiif leg derricks and more particularly to improvements therein which facilitate use and operation of the derricks.

The stilf leg derricks presently in use utilize specially made narrow base booms which are pivoted directly to an upright mast that is rotatably mounted with respect to the ground. The booms, because of the narrow base, must be braced with sway rods for support when the boom is swung during use.

The stiff legs or back braces on conventional derricks are not infinitely adjustable or movable with respect to each other within the normal angular range.

The stiff leg derrick of the present invention, in the form as disclosed, illustrates a unit wherein a standard wide base crane boom can be utilized. An unique strut arrangement is used to pivotally support the boom about an axis spaced outwardly from the mast. All or" the vertical components of the boom swing loads are transmitted directly to the mast through the strut assembly and, in addition, at short radii the restraining moment of the boom tackle is increased, thereby increasing the lifting capacity of the boom.

The stiff legs or back supports and the stiff leg sills used with the supports are pivotally mounted about the mast axis so that they can be angularly adjusted with respect to each other in order to fit particular terrain when the boom is installed.

It is an object of the present invention to present a stiff leg derrick that has more stability, greater load ca pacity and has angularly adjustable stilf legs.

In the drawings,

FIG. 1 is a side elevational view of a stiff leg derrick made according to the present invention;

FIG. 2 is a fragmentary top plan view of the device of FIG. 1 with parts in section and parts broken away; and shown with the still leg assemblies rotated 45 de grees;

FIG. 3 is a fragmentary enlarged side elevational view of a base portion of the device of FIG. 2 showing means for attaching stiff leg sills to the mast assembly;

FIG. 4 is a fragmentary enlarged side elevational view of the mast top assembly with parts in section and parts broken away;

FIG. 5 is a sectional view taken as on line 5-5 in FIG. 4;

FIG. 6 is a fragmentary enlarged side elevational view of a base portion or" a mast assembly with parts in section and parts broken away;

FIG. 7 is a schematic side elevational view of a sheave and hoist drum arrangement utilized with the device of the present invention; and

FIG. 8 is a schematic top plan view of the device of FIG. 7.

Referring to the drawings and the numerals of reference thereon, a stiff leg derrick indicated generally at 19 includes a base 11, which, in the normal circumstances, will be the ground, on which a mast support 12 is mounted. The mast support 12 has a bearing assembly 13 mounted thereon and the bearing assembly supports an upright mast assembly 14. The mast assembly is rotatably mounted with respect to the mast support. A gudgeon pin, 15 is fixedly mounted to the top of the mast assembly and the axes of the pin and mast are coincidental. A first collar 16 is mounted on the gudgeon pin and a second collar 17 is rotatably mounted on the pin above the collar 16. The collars 16 and 17 are rotatably mounted on the pin and with respect to each other on suitable bearings 18. Each of the collars 16 and 17 has an ear 20 to which a separate stiff leg or back brace 21 is pivotally mounted, as at 22.

As shown, the stiff legs are positioned at substantially 90 degrees to each other, although their angular position with respect to each other can be varied. The stilf legs 21 extend downwardly and are each mounted as at 23 to a separate bracket 24. The brackets 24 are anchored to supports 25 that in turn are fixedly attached with respect to the base 11, or the ground at a location spaced from the mast support.

Each of the brackets 24 has a separate sill 26 fixedly attached thereto. The sills 26 extend substantially paral lel to the ground or base 11, and each sill has a fixedly attached bracket 27. The brackets are rotatably mounted over the mast support 12 and are supported on a shoulder 28. The sills are identical in construction except one is inverted in assembly to prevent interference between the brackets.

The stiff leg, the sills and brackets 24 together comprise stitf leg assemblies. Thus, it can be seen, as collars 16 and 17 are rotatably mounted on the gudgeon pin and the sills 26 are rotatably mounted to the mast support, each of the stilf leg assemblies can be rotated as a unit about the axis of the mast. The two stilf leg assemblies can be adjusted rotationally with respect to each other as Well as with respect to the mast to make adjustments necessary to fit particular locations at which the stiff leg derrick must work.

The mast assembly 14 includes a bottom bearing carrier 29 to which a mast pole 31 is attached. A bull wheel 30 is fixedly attached to the mast assembly 14 with four braces 32 that are fastened from the mast pole 31 to the bull Wheel rim and a pair of legs 34 that are fastened to the bearing carrier 29 as at 35. The hull wheel is connected directly to the mast and rotates with the mast. Additional bracing and supports are used if necessary.

A pair of strut assemblies illustrated generally at 33 are provided to support the boom. Each strut assembly includes one of the bottom legs 34 which is mounted to the bearing carrier. A separate bracket 36 is fixedly attached to an outer end of each leg 34. The brackets are also attached to the bull wheel 30. A strut member 37 is pivotally mounted as at 38 to an upwardly extending portion of each bracket 36 and each strut member extends to be pivotally mounted as at 41 to one of a pair of plates 42, 42 that are fixed to an upper portion of the mast pole 31.

A boom assembly 43 is pivotally mounted as at 44 bei tween the brackets 36. The boom assembly, as disclosed,

is a conventional crane boom having a wide base portion 45 so that the pin at pivot 44 gives adequate support to the boom during slewing or swinging of the mast and boom assembly during use. Therefore the sway rods present in all stiff leg derricks of conventional design are eliminated entirely.

A mast bail 48 is mounted on pin 15 and supports a tackle block-46 which in turn supports a plurality of sheaves 47 over which a cable 56 is mounted. The cable 50 is also mounted over sheaves 51 that are rotatably mounted in a block 52 which in turn is connected to a boom pendant 53. The boom pendant in turn is attached as at 54 to the upper or outer end 55 of the boom. The cable 50 extending between sheave assemblies 51 and 47 has a control length 56 extending over a sheave 57 rotatably mounted between plates 42 and then is threaded downwardly through the interior of tubular mast pole 31 to a sheave 70 in a lower sheave assembly 60 which is awar /s 9 a rotatably mounted on mast support 12. Control length 56 extends outwardly to a suitable hoist drum 77.

The boom control line or tackle can be as many parts as necessary in order to support the load on the boom.

A load line 61 extends over a first load sheave 62 rotatably mounted at the outer end 55 of the boom 43 and supports a hook 63. In addition a sheave assembly 64 may be utilized in order to have as many working parts on the load line as necessary. 7

The load line 61 also extends over a sheave rotatably mounted on the same axis as sheave 57 and then extends downwardly through mast 14 to a sheave 71 in the sheave assembly 60 which is rotatably mounted on mast support 12. The load line also can be controlled by a hoist drum 78.

All of the points of rotation, for example, the bearing assembly 13 and collars 16 and 17 are mounted on antifriction bearings which take both radial and thrust loads.

The bearing assembly 13 includes a lower bracket 82 that is mounted directly on base 12. An upper bracket 83 is mounted over the lower bracket. A bearing retainer 84 having a part spherical outer surface is clamped between the lower and upper brackets. The brackets are fastened together and to mast support 12 with a plurality of bolts 85.

The bearing retainer is used to mount a bearing 86 which is also mounted to bearing carrier 29, to which the mast pole 31 is attached. The bearing is held in place within retainer 84 with a lock ring 88. The bearing 86 is designed to take both radial and thrust loads. The mast pole thus is bearing supported and rotates easily with respect to the base.

Shown schematically in FIGS. 7 and 8 is an arrangement for preventing interference between the load line, the boom hoist line, and an auxiliary load line which may be utilized with the derrick. As can be seen the sheave assembly as comprises three separate sheaves, 70, 71 and 72 which are of different outside diameter. The sheaves are all rotatably mounted about the same axis 73. The lines 61, 6 and an auxiliary load line 74 are mounted over the perspective sheaves. The lines then extend to first, second and third hoist drums 77, 78 and 79, respectively as can be seen the drums 77, 78 and 7? are arranged in a waterfall, with the first drum 77 positioned below the second drum 78 and the second drum 78 positioned below the third drum 79. In this manner the lines 55, 61 and 74 are vertically spaced from each other. Thus as the cables or lines 56, 61 and 74 move back and forth on their respective drums in directions as indicated by double arrow 84) there is no interference between the'liues although they are guided around sheaves which are very close together. This arrangement wherein the lines are vertically spaced on the waterfall drums and are guided on sheaves of different diameters prevents fouling of the lines during use.

The mast assembly 14 is rotated by actuating the bull wheel. The bull wheel has a cable 68 mounted around the outer periphery thereof. The cable 68 is termed a slewing line and is powered through any conventional hoist arrangement. The slewing line 68 is mounted over a pair of guide sheaves d9, 6% which are rotatably mounted adjacent the bull wheel. By actuating the slewing line in opposite directions the bull Wheel can be made to rotate and this in turn will cause the mast assembly, boom and associated parts to rotate also.

The wide base boom, which is mounted between the brackets 36, 36 eliminates the need for sway rods which are conventionally found on stiff leg derricks. Also the strut assembly 33 is made such that the vertical components of the load induced from the boom during swinging or hoisting movements are transferred directly to the mast through the strut members 37. This largely eliminates the bending moment on the mast which was present in conventional derricks wherein the mast is pivotally mounted adjacent the base of the boom.

Thus the improvements in the stiff leg derrick makes the unit adaptable to many more locations, much easier to assemble, and also increase the stability of the boom as well as the lifting capacity for the same size mast. The wide base mounting permits use of conventional crane booms thus reducing cost through the use of standard parts.

Formerly, the sway rods transferred the swing load from the boom to the attachment points for the sway rods, usually on the bull wheel. As the sway rods extended from the plane of the bull wheel at an angle, there were always vertical reactions to the swing load absorbed by the bull wheel. This vertical reaction forms a couple transferred by the bull wheel to the mast, thus exerting a bending moment on the mast. This bending moment could become very large and limits the swing capacity of the stiff leg derrick when transporting a load. Through the use of a wide base boom and the strut assembly these vertical swing loads are transferred directly to the mast without large moments being built up. Thus the bending of the mast is reduced and the unit is able to handle larger loads than similarly sized conventional units.

The rotatable mounting of the stiff leg assemblies increases the versatility of the unit and makes it adapted for more uses than before. This is particularly important where uneven terrain and other unusual situations are encountered.

As shown in dotted lines in FIG. 1, conventional booms are pivotally mounted to the mast directly at the base thereof. When the boom is working on a short radius with respect to the base of the boom, the amount of load that can be lifted by the boom is limited by the capacity of the boom cables. With the present unique design utilizing the strut assembly for supporting the boom, this moment is increased and therefore the lifting capacity of the boom, at close radii, is also increased.

What is claimed is:

1. A derrick including:

a base,

a support member on said base,

an upright mast assembly rotatably mounted with respect to the support member,

strut means fixedly mounted on said mast adjacent the top thereof and having bracket means thereon positioned adjacent the ground,

a wide base boom pivotally mounted to said attachment bracket means about a substantially horizontal axis that is spaced outwardly from the mast a substantial distance in the direction of normal extension of the boom,

means to control the angular position of said boom with respect to said mast,

a pair of back brace assemblies each comprising a sill rotatably mounted with respect to the support member and a brace member fixedly attached to said sill at position spaced from said mast and rotatably mounted to a top portion of said mast,

means to rotate said mast and boom unit with respect to said back brace assemblies and said support about the mast axis, and

brace means fixed to said bracket means and extending to be fixed to said mast adjacent the bottom portions thereof.

2. The combination as specified in claim 1 wherein said means to rotate said mast and boom comprises a bull Wheel mounted for rotation with said boom and mast, said bull Wheel being of substantial diameter and the plane of movement of said bull wheel being substantially horizontal, the pivotal axis of said boom being adjacent the peripheral edge of the bull wheel.

3. The combination as specified in claim 2 wherein the operations of said derrick are controlled with a plurality of lines, said lines being mounted over guide members adjacent the bottom of the mast, each guide memher being positioned a different distance from a reference plane than the others, and a separate drum for controlling the lines, said drums each controlling one of said cables, the point of contact between each cable and its respective control drum being spaced from the reference plane in the same relative position as that cables guide member with respect to the other cables.

4. A stilt leg derrick including: a base, a support member on said base, an upright mast rotatably mounted with respect to the support member, a bull wheel member fixed to rotate with said mast and positioned adjacent the bottom of said mast, a wide base boom, bracket means to pivotally mount said boom about a substantially horizontal axis forming a chord line adjacent the peripheral edge of the bull wheel, said axis being spaced a substantial distance from the mast axis in a horizontal direction, means to control the angular position of said boom with respect to said mast, strut means fixedly attached to said bracket means and to said mast, at least one back brace assembly rotatably mounted with respect to said support member and said mast and anchored to said base at position spaced from said support, andmeans to rotate said mast and boom with respect to said back brace and said support.

5. The combination as specified in claim 4 wherein the angular position of said boom is controlled with a boom control line, a hoist line mounted on said boom for lifting heavy loads, and an auxiliary hoist line mounted on said boom, said auxiliary hoist line, said hoist line and said boom control line being mounted on a plurality of sheaves rotatably mounted about the same axis adjacent the base of the mast, said sheaves being of different outside diameters, said lines being mounted over said sheaves, and hoist means for controlling said sheaves, said hoist means having three hoist drums aligned with each other in direction of travel of said lines and being vertically offset, the line on the largest sheave being'mounted on the lowermost of said drums, the line on the intermediate size sheave being mounted on the intermediate drum and the line on the smallest diameter sheave being mounted on the highest drum.

References Cited in the file of this patent UNITED STATES PATENTS 967,203 Lambert Aug. 16, 1910 1,856,907 Chapman May 3, 1932 2,051,497 Sasgen et al Aug. 18, 1936 

1. A DERRICK INCLUDING: A BASE, A SUPPORT MEMBER ON SAID BASE, AN UPRIGHT MAST ASSEMBLY ROTATABLY MOUNTED WITH RESPECT TO THE SUPPORT MEMBER, STRUT MEANS FIXEDLY MOUNTED ON SAID MAST ADJACENT THE TOP THEREOF AND HAVING BRACKET MEANS THEREON POSITIONED ADJACENT THE GROUND, A WIDE BASE BOOM PIVOTALLY MOUNTED TO SAID ATTACHMENT BRACKET MEANS ABOUT A SUBSTANTIALLY HORIZONTAL AXIS THAT IS SPACED OUTWARDLY FROM THE MAST A SUBSTANTIAL DISTANCE IN THE DIRECTION OF NORMAL EXTENSION OF THE BOOM, MEANS TO CONTROL THE ANGULAR POSITION OF SAID BOOM WITH RESPECT TO SAID MAST, A PAIR OF BACK BRACE ASSEMBLIES EACH COMPRISING A SILL ROTATABLY MOUNTED WITH RESPECT TO THE SUPPORT MEMBER AND A BRACE MEMBER FIXEDLY ATTACHED TO SAID SILL AT POSITION SPACED FROM SAID MAST AND ROTATABLY MOUNTED TO A TOP PORTION OF SAID MAST, MEANS TO ROTATE SAID MAST AND BOOM UNIT WITH RESPECT TO SAID BACK BRACE ASSEMBLIES AND SAID SUPPORT ABOUT THE MAST AXIS, AND BRACE MEANS FIXED TO SAID BRACKET MEANS AND EXTENDING TO BE FIXED TO SAID MAST ADJACENT THE BOTTOM PORTIONS THEREOF. 